Copyright Goodheart-Willcox Co., Inc. Chapter 18 Concrete Flatwork and Formed Shapes 405 Cored slabs provide a flush ceiling with minimum depth required for the roof or floor system. See Figure 18-53. Slab thicknesses range from 4″ to 12″ in increments of 2″. A variety of widths are available, including 1′-4″, 1′-8″, 2′-0″, 3′-4″, and 4′-0″. All sizes are not available in a single core style. Lengths gener- ally range from 12′ to 40′, but the length of a partic- ular slab depends on the thickness, width, and rein- forcing. Generally, the thicker the slab, the longer the length available. Precast concrete window walls may be cast as curtain walls or loadbearing walls. Forms or molds used to produce complicated designs are made from plastic, wood, or steel. These forms are custom units and must be designed by architects or engineers. Typically, fiberglass molds are used for smooth concrete with sculptured mullions (wall members supporting a window). Precast window walls or wall openings can be one-story or multistory. See Figure 18-54. Precast window walls can even be preglazed (the glass installed) at the plant. Kawneer Company, Inc. Figure 18-54. A precast panel is being raised by a crane to be positioned in its final location in the structure. Goodheart-Willcox Publisher Figure 18-53. Hollow-core slabs are low in cost and widely produced. Depths range from 4″ to 12″. Widths are available from 16″ to 48″. Spans possible with cored slabs are up to 50′, but generally under 35′.